1. Field of the Invention
This invention relates to a method and apparatus for spraying the interior surface of a cup-shaped type of vessel for receiving molten metal having a refractory lining that is exposed to elevated temperatures over a long period of use that results in deterioration of the interior refractory lining of said vessel. This invention also relates to an apparatus for spraying said interior refractory linings of said vessel. It particularly relates to a nozzle assembly supported on the sill or top edge of the vessel or in one of a plurality of windows that are circumferentially spaced and that extend through the side wall of a refractory wall. Particularly, the present invention relates to an operation combining two spraying methods, the first spraying method using materials that are sprayed onto an interior surface portion that requires removal of scale. The second spraying method is used to apply a new refractory coating onto the cleaned surface of the wall of the refractory body.
2. Description of the Prior Art
Refractory lined bodies used in the iron and steel industry for carrying, holding and pouring molten metal are normally exposed to elevated temperature over a long period of use. The interior refractory surfaces of these refractory bodies deteriorate with such extended use. Therefore, it is necessary to either replace or repair any deteriorated interior surface.
Initially, an interior surface was repaired by laying refractory brick over the deteriorated surface. However, the labor cost of brick laying was so exorbitant that the refractory industry has developed high temperature plastic refractories having a pliable construction to permit shaping of the material to the contour of the interior surface being relined. The preshaped plastic refractory material is installed by pneumatic hammers to mold the refractory lining to the contour of the interior surface. It is also known to utilize a heat resistant castable ceramic refractory that is installed on the interior surface in a manner similar to the installation of a conventional castable cement. This requires considerable labor and the erection of frames to contain the castable refractory cement until the latter is cured.
More recently, the deteriorated refractory surface of a blast furnace or the like has been reconditioned and repaired by the gunning application of a refractory material that is formed by mixing a dry mix of refractory binder and aggregate propelled through a hose by a stream of compressed air to a nozzle into which a wetting agent, such as water, is supplied to mix with the dry refractory to form a mix. This mix is sprayed onto the interior surface.
Typical gunning apparatus of the prior art includes U.S. Pat. Nos. 4,253,646 to Goto et al; 4,272,020 to Allison; 4,301,998 to Rodway and 4,494,737 to Rymarchyk, Jr. et al. These patents show a feed pipe for feeding the slurry in a gunning assembly in the direction of the axis of the refractory body whose interior surface is to be sprayed. It is necessary to change the direction of movement of the sprayed slurry so that the path of the movement of the slurry is turned in a direction oblique to the axis of the supply pipe when the slurry reaches its interior end portion through nozzles that extend angularly from the pipe interior end portion to direct the slurry against the interior surface to be sprayed.
Other typical gunning apparatus, such as depicted in U.S. Pat. Nos. 4,106,760 to Kono et al; 4,222,522 to Kubo et al; and 4,313,565 to Focant, pivotally support a slurry supply pipe on a movable car that supports the axis of pivoting of the slurry and must of necessity be a relatively massive counter-weighted car in order to maintain its balance for orientation.
It is also known to form an interior refractory wall within a refractory lined vessel by establishing a form within the vessel and providing a vibrating hopper above the vessel that feeds particulate refractory materials to the space between the form and the interior wall of the vessel shell and the material deposited in said space is compacted by tamping to form a solid cover of refractory material for the interior vessel wall. A typical device of the latter type is disclosed in U.S. Pat. No. 4,534,730 to Kraus. A drawback of this material is the tendency of the particulate refractory material to form a dust and the expensive equipment required for avoiding the formation of the dust and the expensive labor cost for removing the form after the refractory wall has been completed.
It is known in the prior art to dry newly lined refractory hearths and walls of vessels by use of directional devices. These directional devices direct the drying material in a predetermined direction into the vessel. A typical device of this type is disclosed in U.S. Pat. No. 3,610,183 to Kolboy et al. A drawback of this apparatus is that the directional devices are not movable once inserted and cannot be used for a relatively small portion of the vessel.
The methods of applying the material to be sprayed in the form of a liquid or slurry is superior to any method involving compacting a pulverulent material because of the health problems inherent in the formation of dust. However, in the application of liquid or slurry of materials through an elongated pipe, the force by which the liquid or slurry may be imparted is limited when the liquid or slurry is propelled through a delivery pipe - nozzle system that is not straight throughout its entire length. Therefore, it is necessary to provide a higher pressure imparting means to cause the liquid or slurry to be applied at a much higher pressure to overcome the loss of force that occurs when the liquid or slurry is caused to turn at an angle to the initial direction of its propulsion.
It is also beneficial to maintain the temperature of a refractory lined vessel within the operating temperature range to minimize the power loss needed for removing unwanted scale and applying a new coating of refractory material that bonds to the cleaned interior surface of a refractory lined vessel, such as a blast furnace, particularly when the refractory lined vessel operates at an extremely high temperature range. The use of concentric pipes in groups within a high temperature atmosphere is detrimental to the continued operation of the spray apparatus that is used to clean or reline an interior surface of such a refractory body in a high temperature environment.